Prenatal genetic screening tests: benefits & risks

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GENETICS can influence the color of a baby’s eyes and hair, but it can also affect the development of certain birth defects or genetic disorders. That’s why women are routinely offered a variety of genetic screening tests in the first and second trimesters of pregnancy to evaluate the risk for these potential problems in their unborn baby.
Screening tests can determine whether the baby is more or less likely to have certain birth defects or genetic disorders, which may be inherited. Screening results along with other risk factors, such as a woman’s age and a couple’s ethnic background and family history of genetic disorders, are used to calculate the odds that the fetus might be born with certain genetic disorders, such as Down syndrome, cystic fibrosis, Tay-Sachs disease, or sickle cell anemia. Birth defects affect 1 in 33 babies — about 3 percent of all babies — born in the United States each year, according to the Centers for Disease Control and Prevention (CDC). Birth defects can occur at any point during pregnancy, but most of them occur during the first trimester, when the baby’s organs are forming, the CDC says. Genetic screening is offered to all pregnant women, and it’s usually discussed during the first prenatal visit, said Dr. Andrea Greiner, a maternal and fetal medicine specialist at the University of Iowa Hospitals and Clinics. “It’s optional, but not required.”
Most women get prenatal genetic testing to know what the risk is before the baby is born, Greiner said. They would rather know the information during pregnancy than at birth so they can make plans and decisions ahead of time or gain further knowledge, she explained. “Every woman wants to believe that her pregnancy is normal and uncomplicated,” Greiner told Live Science. If a pregnant woman chooses to have genetic screening, there is a possibility that the results could come back abnormal so it’s important to think about how this information might affect her, she noted.
But not all genetic screening occurs while a woman is expecting. In some situations, it may be done before becoming pregnant. For example, during pre-conception genetic screening, carrier tests can be done to determine whether the mother or father carry a certain gene for genetic disorders that might run in families, such as cystic fibrosis and sickle cell anemia, and could be passed on when the couple conceives. A common misconception among some pregnant women is that the only reason to do genetic screening and diagnostic testing is if they were going to have an abortion because of a positive result, Greiner said. But that’s not the case, she said.

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